An embodiment of the present invention is directed to an apparatus for mechanical transmission, and in particular an apparatus having the need for rotatable moving parts relative to each other or in space. An embodiment of the present invention can be applied, but not exclusively, in the field of medical imaging. An embodiment of the present invention can be used, for example, to carry out a radiographic or radioscopic examination or applications. Still further, an embodiment of the invention is directed to an X-ray apparatus and in particular a mobile X-ray apparatus.
There are known mobile X-ray machines comprising mobile parts enabling them to rotate in different directions about a patient. These mobile parts thus enable the orientation of an X-ray beam, so as to analyze a given part of an object to the examined, such as a patient's body. In one example, the orientation of the X-ray beam is useful in that it can be aligned very precisely in one direction of the blood vessel to be analyzed.
There are known apparatus that comprise several driving units to move mobile parts in space. Each of these driving units comprises at least one motor, one belt and one reduction gear. In general, the reduction gear is fastened to a mobile part and is connected to the motor by means of the belt. These driving units limit the total speed of the motor so that the mobile parts of the apparatus move at a limited speed. In a radiographic apparatus, for example, to orient the X-ray beam, high speed is unnecessary and may degrade precision in the movement of the beam.
However, with such driving units, the movements of the mobile parts of the apparatus are not as precise as desired. For example, each part of the X-ray apparatus introduces additional clearance or looseness between itself and the parts to which it is fastened. Since the driving unit comprises at least three parts, there are numerous clearances between these parts. These clearances notably diminish the total precision of the apparatus. These clearances may therefore falsify many movements of the mobile parts of the apparatus.
Furthermore, given the number of parts and the need to minimize the clearances, the assembling of the driving units is often difficult.
In addition, the motors and the reduction gears that comprise the driving unit are solid elements that make it difficult to pass cables and power supply wires into the apparatus. Typically, the cable pass around the reduction gears and motors to connect the elements together. It is therefore difficult to assemble the different elements of the apparatus by means of cables. At certain times, spaces have to be provided along particular parts for the passage of the cables inside the apparatus. The solid nature of the motors therefore constitutes another problem of assembly.
Furthermore, the cables must pass around the motor and/or the reduction gear may raise problems of the premature wearing-out of these cables. In such a configuration, the cables may get folded when the apparatus is in particular positions.